Two new drugs for men with advanced prostate cancer, which have appeared in the last year, give hope to extend the life of patients and improve its quality, according to experts in Chicago during the world’s largest oncology congress.
The 47th annual meeting of the American Society of Clinical Oncology (ASCO), held on June 3-7, gathered around 30 people every year. doctors, scientists and representatives of the pharmaceutical industry.
Dr. Howard I. Scher of the Memorial Sloan-Kettering Cancer Center in New York said during a press conference that the outlook for men with castration-resistant advanced prostate cancer (until recently referred to as hormone refractory cancer) has improved significantly over the past year. It is a cancer of the prostate that progresses and metastasizes even though the patient’s blood testosterone has been lowered to zero with hormone therapy. Testosterone stimulates the growth of prostate cancer at every stage of its development.
Two new drugs registered in the last year extend the survival of patients whose disease has progressed due to the ineffectiveness of hormone therapy and the currently available chemotherapy. Each of them has a different mechanism of action, so when the first one stops working, it will probably be possible to reach for another one with the hope of further benefit for the patient – emphasized in an interview with PAP Dr. Iwona Skoneczna from the Oncology Center in Warsaw, who conducted the poster session in Chicago on prostate cancer.
One of them – cabazitaxel – is a new type of chemotherapy. It is now formally available to patients in Europe, including Poland, because on March 20 it was authorized by the European Medical Agency (EMA). The second drug – abiraterone – which is a new form of hormone therapy, has so far been approved in the US.
As Dr. Skoneczna recalled, advanced prostate cancer is referred to when the tumor in the prostate is so large that surgery or radiotherapy cannot be used, or when it has metastasized to lymph nodes or distant organs – most often bone. In these cases, hormone therapy is used, which reduces the level of testosterone in the blood to zero. However, it ceases to be effective over time.
A more aggressive course of the disease is usually found in patients who become ill at a younger age, e.g. between 40 and 60 years of age, the oncologist noted. According to her, in recent years there has been an increasing number of cases of prostate cancer among men in this age group.
So far, the only drug that – as studies have shown – prolonged the survival of patients with prostate cancer in the stage of hormonal therapy resistance by several months was docetaxel. It is a cytostatic from the group of taxanes, i.e. compounds that block cell division by affecting microtubules – filaments that regulate the distribution of genetic material to daughter cells. If the disease progressed after taking docetaxel, the doctors could not offer the patients much.
In 2010, the ASCO presented a study that showed that in patients with castration-resistant prostate cancer, administration of a new taxane – cabazitaxel – reduced by 30 percent. risk of death compared to the group treated with the older cytostatic mitoxantrone. The latest analyzes presented in Chicago show that the benefit of cabazitaxel after prior docetaxel treatment is an average of 4 additional months of life for patients. The main side effects of this drug are decreased immunity leading to infection, nausea and vomiting, fatigue.
Dr. Skoneczna reminded that prostate cancer that progresses despite hormone treatment has so far been defined as hormone-resistant. In fact, studies have shown that the term is imprecise, because although the patient’s blood lacks testosterone, tumor cells at the primary site and at the site of metastasis still produce testosterone. These amounts of the hormone can stimulate the growth of cancer.
The way to do this turned out to be a new drug classified as hormone therapy – arbiraterone. It has an innovative mechanism of action – it blocks the synthesis of testosterone in cancer cells by inhibiting the enzyme CYP17.
A study of 1195 patients with castration-resistant prostate cancer who had previously received docetaxel treatment found that abiraterone reduced the risk of death by 35%. and prolongs survival time by an average of 4 months compared to the control group treated with placebo.
A frequent complication of hormone therapy currently used in prostate cancer is the reduction of bone tissue density (osteopenia), which may lead to the development of osteoporosis and fractures. Additionally, bones may be weakened by the presence of metastases.
Recent studies in Chicago show that abiraterone halves (from 150 days to 301 days) the time to the first skeletal event, such as a vertebral fracture, spine compression, or the need for pain-relieving bone radiation.
Joint swelling, hot flushes, diarrhea, urinary tract infections, potassium deficiency, cough and hypertension were among the most common side effects of abiraterone.
Dr. Skoneczna recalled that in April 2010, the first anti-cancer vaccine for castration-resistant prostate cancer (sipuleucel-T) was registered in the US. It prolongs the survival of patients by an average of 4 months compared to placebo. For now, however, it is not approved for the European market, and besides, it is very expensive (over USD 90), because it is developed separately for each patient from their own immune cells.
According to Dr. Skoneczna, perhaps in the future studies will be conducted to assess the order in which to use new drugs in individual patients, so that they give the best results. Prostate cancer is in fact a very heterogeneous group of cancers and we are currently unable to predict which sequence of therapy will be most effective in a given patient, the researcher noted.
Currently, PSA (i.e., prostate-specific antigen) levels are used to evaluate treatment effects and to predict disease progression. The research presented in Chicago by Dr. Scher shows that the new, more accurate indicator will be the number of cancer cells in the peripheral blood. Research is also underway to identify genetic indicators.
Prostate cancer is one of the most common malignant neoplasms in men. In Poland, it ranks second in terms of both the number of cases and mortality from neoplastic diseases among men. In 2008, 3892 deaths due to prostate cancer were recorded in our country, which is approx. 50 percent. the number of new cases, which in the same year amounted to 8268. However, in the US this percentage is equal to 10 percent. – emphasized Dr. Skoneczna. In her opinion, it is largely related to the fact that in Poland prostate cancer is often diagnosed too late.
From Chicago Joanna Morga (PAP)